{"gene":"P3H4","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2014,"finding":"SC65 (P3H4) is an endoplasmic reticulum-resident protein, not a nuclear or synaptonemal complex protein in somatic cells; its loss results in progressive osteopenia and a non-cell-autonomous increase in osteoclastogenesis, establishing SC65 as a negative regulator of bone resorption.","method":"Subcellular fractionation and immunofluorescence localization; Sc65 knockout mouse model with bone phenotyping (microCT, histomorphometry)","journal":"Journal of bone and mineral research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO mouse with defined cellular phenotype and direct ER localization experiment, single lab, two orthogonal methods","pmids":["23959653"],"is_preprint":false},{"year":2016,"finding":"SC65 (P3H4) forms a complex in the ER with prolyl 3-hydroxylase 3 (P3H3); this complex regulates lysyl hydroxylase 1 (LH1) activity on collagen, potentially through interactions with LH1 and/or cyclophilin B. Loss of Sc65 destabilizes this complex, causing reduced collagen lysine hydroxylation and abnormal collagen cross-linking, leading to low bone mass and skin fragility.","method":"Sc65 knockout mouse model; co-immunoprecipitation of ER complex components; mass spectrometry-based collagen modification analysis; skeletal and connective tissue phenotyping","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP identifying complex members, KO mouse with defined molecular and tissue phenotype, multiple orthogonal methods","pmids":["27119146"],"is_preprint":false},{"year":2017,"finding":"SC65 (P3H4) and P3H3 act in the same pathway to hydroxylate lysines specifically at helical domain cross-linking sites in collagens I, across multiple tissues (skin, bone, tendon, aorta, cornea); neither SC65 nor P3H3 loss affects prolyl 3-hydroxylation at any known 3-hydroxyproline site. Loss of either protein alters divalent aldimine cross-link chemistry and reverses the HP/LP mature cross-link ratio in bone, phenocopying EDS VIA (PLOD1 deficiency).","method":"Tandem mass spectrometry on collagen from Sc65-/- and P3h3-/- mouse tissues; SDS-PAGE analysis of collagen cross-linked trimers; quantitative cross-link analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — quantitative MS-based substrate mapping in two independent KO models with orthogonal biochemical validation, replicated across multiple tissue types","pmids":["28115524"],"is_preprint":false},{"year":2020,"finding":"ETV4 directly binds the promoter region of P3H4 and activates its transcription in bladder cancer cells; P3H4 knockdown inhibits bladder cancer cell proliferation, cell cycle progression, migration, and invasion in vitro and tumor growth in vivo, and overexpression of ETV4 rescues the inhibitory effects of P3H4 silencing.","method":"Chromatin immunoprecipitation (ChIP) and promoter reporter assays for ETV4 binding; shRNA knockdown of P3H4; rescue experiments with ETV4 overexpression; xenograft tumor model","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating direct promoter binding, genetic rescue experiment, in vivo xenograft, single lab","pmids":["32018225"],"is_preprint":false},{"year":2022,"finding":"P3H4 interacts with EGFR to promote malignant progression (metastasis and proliferation) of lung adenocarcinoma, with P3H4 modulating metabolic substances in this context.","method":"Co-immunoprecipitation/interaction assay between P3H4 and EGFR; P3H4 knockdown/overexpression in LUAD cell lines; in vivo tumor models","journal":"Cancers","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP/pulldown reported in abstract without detailed mechanistic follow-up, single lab, limited methodological detail","pmids":["35805016"],"is_preprint":false},{"year":2023,"finding":"METTL3 (an m6A methyltransferase) regulates the mRNA stability of P3H4 in bladder cancer; METTL3 knockdown reduces P3H4 mRNA half-life, and overexpression of P3H4 rescues the inhibitory effects of METTL3 knockdown on bladder cancer cell proliferation, migration, invasion, and EMT.","method":"RNA stability assays measuring P3H4 mRNA half-life after METTL3 knockdown; shRNA knockdown and overexpression rescue experiments; in vivo xenograft with IHC","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA stability assay directly measuring mRNA half-life, genetic rescue experiment, in vivo validation, single lab","pmids":["37979898"],"is_preprint":false},{"year":2025,"finding":"P3H4 knockdown in hepatocellular carcinoma cells suppresses PI3K/AKT pathway phosphorylation and inhibits proliferation, invasion, and glycolysis (reduced glucose consumption, lactate, and ATP production).","method":"shRNA knockdown of P3H4; CCK8 viability assay; glycolysis detection kit measuring glucose/lactate/ATP; western blot for PI3K/AKT phosphorylation; nude mouse xenograft with IHC","journal":"International journal of genomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, pathway placement inferred from phosphorylation changes without direct mechanistic link to P3H4's enzymatic/binding activity","pmids":["41220593"],"is_preprint":false}],"current_model":"P3H4 (SC65) is an ER-resident, non-enzymatic member of the leprecan family that forms a stable complex with prolyl 3-hydroxylase 3 (P3H3) and cyclophilin B; this complex is required for lysyl hydroxylase 1 (LH1) to hydroxylate lysine residues at helical cross-linking sites in fibrillar collagens across multiple tissues, and loss of P3H4 causes collagen lysine under-hydroxylation, aberrant cross-link chemistry phenocopying EDS VIA, low bone mass, and skin fragility, while in cancer contexts its transcription is driven by ETV4 and its mRNA stability is regulated by METTL3-mediated m6A modification."},"narrative":{"mechanistic_narrative":"P3H4 (SC65) is an endoplasmic reticulum-resident protein that functions in collagen post-translational modification rather than in the nuclear/synaptonemal roles once attributed to it [PMID:23959653]. In the ER it forms a stable complex with prolyl 3-hydroxylase 3 (P3H3), and this complex regulates the activity of lysyl hydroxylase 1 (LH1) on collagen, potentially through interactions involving LH1 and cyclophilin B [PMID:27119146]. P3H4 and P3H3 act together specifically to hydroxylate lysines at helical-domain cross-linking sites in fibrillar collagens across skin, bone, tendon, aorta, and cornea, without affecting prolyl 3-hydroxylation; loss of either protein alters divalent aldimine cross-link chemistry and reverses the bone mature cross-link ratio, phenocopying EDS VIA (PLOD1 deficiency) [PMID:28115524]. Consistent with this biochemical role, loss of P3H4 destabilizes the ER complex and produces collagen lysine under-hydroxylation, low bone mass, and skin fragility, with progressive osteopenia driven by non-cell-autonomous increased osteoclastogenesis [PMID:23959653, PMID:27119146]. In cancer contexts, P3H4 transcription is directly activated by ETV4 in bladder cancer, where it supports proliferation, cell-cycle progression, migration, and invasion [PMID:32018225], and its mRNA stability is regulated by METTL3-mediated m6A modification [PMID:37979898].","teleology":[{"year":2014,"claim":"Established that SC65/P3H4 is an ER-resident protein in somatic cells rather than a nuclear synaptonemal-complex component, reassigning its cellular compartment and linking it to skeletal homeostasis.","evidence":"Subcellular fractionation and immunofluorescence plus Sc65 knockout mouse bone phenotyping (microCT, histomorphometry)","pmids":["23959653"],"confidence":"Medium","gaps":["Molecular mechanism connecting ER localization to the osteoclast phenotype not defined","Non-cell-autonomous signal driving osteoclastogenesis not identified"]},{"year":2016,"claim":"Defined the molecular partnership: SC65/P3H4 forms an ER complex with P3H3 that regulates LH1-mediated collagen lysine hydroxylation, explaining the bone and skin phenotypes.","evidence":"Co-immunoprecipitation of ER complex components, MS-based collagen modification analysis, and connective-tissue phenotyping in Sc65 knockout mice","pmids":["27119146"],"confidence":"High","gaps":["Direct enzymatic role of P3H4 within the complex not established (non-enzymatic scaffold vs. catalytic)","Precise stoichiometry and contributions of LH1 and cyclophilin B unresolved"]},{"year":2017,"claim":"Mapped substrate specificity to helical-domain cross-linking lysines and showed the pathway controls cross-link chemistry, demonstrating that P3H4/P3H3 loss phenocopies EDS VIA.","evidence":"Tandem MS substrate mapping and quantitative cross-link analysis on collagen from Sc65-/- and P3h3-/- mouse tissues across multiple tissue types","pmids":["28115524"],"confidence":"High","gaps":["How the complex confers site-specificity to LH1 at helical sites is unknown","Whether human P3H4 mutations cause an EDS-like disorder not addressed in the corpus"]},{"year":2020,"claim":"Identified an upstream transcriptional driver of P3H4 in cancer, showing ETV4 directly activates P3H4 to support bladder tumor cell growth and invasion.","evidence":"ChIP and promoter reporter assays, shRNA knockdown with ETV4-overexpression rescue, and xenograft tumor model in bladder cancer cells","pmids":["32018225"],"confidence":"Medium","gaps":["Effector mechanism linking P3H4 to proliferation/invasion not defined","Relationship between cancer role and ER collagen function unclear"]},{"year":2022,"claim":"Proposed a non-collagen interaction by reporting P3H4 binding to EGFR in lung adenocarcinoma.","evidence":"Co-immunoprecipitation/interaction assay and knockdown/overexpression in LUAD cell lines with in vivo tumor models","pmids":["35805016"],"confidence":"Low","gaps":["Single Co-IP without reciprocal validation or detailed mechanistic follow-up","Direct vs. indirect EGFR association not established"]},{"year":2023,"claim":"Showed post-transcriptional control of P3H4 in cancer, with METTL3-mediated m6A modification stabilizing P3H4 mRNA to promote bladder cancer phenotypes.","evidence":"mRNA half-life assays after METTL3 knockdown plus knockdown/overexpression rescue and in vivo xenograft with IHC","pmids":["37979898"],"confidence":"Medium","gaps":["Specific m6A sites on P3H4 mRNA not mapped","Reader protein mediating stabilization not identified"]},{"year":2025,"claim":"Linked P3H4 to a signaling/metabolic output in hepatocellular carcinoma via PI3K/AKT and glycolysis.","evidence":"shRNA knockdown with viability, glycolysis (glucose/lactate/ATP), and PI3K/AKT phospho-western readouts plus nude mouse xenograft","pmids":["41220593"],"confidence":"Low","gaps":["Pathway placement inferred from phosphorylation changes without direct mechanistic link to P3H4 activity","Connection to ER collagen-modifying function unexplained"]},{"year":null,"claim":"How P3H4's defined ER collagen-modifying role mechanistically relates to its reported oncogenic functions, and whether human P3H4 variants cause connective-tissue disease, remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No reconciliation between scaffolding role in collagen hydroxylation and cancer signaling functions","No human genetic disease evidence in the corpus","No structural model of the P3H4/P3H3/LH1/cyclophilin B complex"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,2]}],"complexes":["ER P3H4-P3H3 collagen-modifying complex"],"partners":["P3H3","LH1","CYCLOPHILIN B","ETV4","METTL3","EGFR"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q92791","full_name":"Endoplasmic reticulum protein SC65","aliases":["Leprecan-like protein 4","Nucleolar autoantigen No55","Prolyl 3-hydroxylase family member 4","Synaptonemal complex protein SC65"],"length_aa":437,"mass_kda":50.4,"function":"Part of a complex composed of PLOD1, P3H3 and P3H4 that catalyzes hydroxylation of lysine residues in collagen alpha chains and is required for normal assembly and cross-linking of collagen fibrils. Required for normal bone density and normal skin stability via its role in hydroxylation of lysine residues in collagen alpha chains and in collagen fibril assembly","subcellular_location":"Endoplasmic reticulum","url":"https://www.uniprot.org/uniprotkb/Q92791/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/P3H4","classification":"Not Classified","n_dependent_lines":47,"n_total_lines":1208,"dependency_fraction":0.03890728476821192},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2},{"gene":"CPSF6","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/P3H4","total_profiled":1310},"omim":[{"mim_id":"617419","title":"PROLYL 3-HYDROXYLASE 4; P3H4","url":"https://www.omim.org/entry/617419"},{"mim_id":"610342","title":"PROLYL 3-HYDROXYLASE 3; P3H3","url":"https://www.omim.org/entry/610342"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"},{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/P3H4"},"hgnc":{"alias_symbol":["SC65","NO55"],"prev_symbol":["LEPREL4"]},"alphafold":{"accession":"Q92791","domains":[{"cath_id":"-","chopping":"25-84_105-142","consensus_level":"medium","plddt":91.8716,"start":25,"end":142},{"cath_id":"-","chopping":"151-201","consensus_level":"medium","plddt":94.2484,"start":151,"end":201},{"cath_id":"-","chopping":"242-378","consensus_level":"high","plddt":92.145,"start":242,"end":378}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92791","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q92791-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q92791-F1-predicted_aligned_error_v6.png","plddt_mean":83.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=P3H4","jax_strain_url":"https://www.jax.org/strain/search?query=P3H4"},"sequence":{"accession":"Q92791","fasta_url":"https://rest.uniprot.org/uniprotkb/Q92791.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q92791/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92791"}},"corpus_meta":[{"pmid":"27119146","id":"PMC_27119146","title":"Sc65-Null Mice Provide Evidence for a Novel Endoplasmic Reticulum Complex Regulating Collagen Lysyl Hydroxylation.","date":"2016","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27119146","citation_count":45,"is_preprint":false},{"pmid":"28115524","id":"PMC_28115524","title":"P3h3-null and Sc65-null Mice Phenocopy the Collagen Lysine Under-hydroxylation and Cross-linking Abnormality of Ehlers-Danlos Syndrome Type VIA.","date":"2017","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/28115524","citation_count":35,"is_preprint":false},{"pmid":"10952778","id":"PMC_10952778","title":"Identification of nucleolar protein No55 as a tumour-associated autoantigen in patients with prostate cancer.","date":"2000","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/10952778","citation_count":25,"is_preprint":false},{"pmid":"23959653","id":"PMC_23959653","title":"Sc65 is a novel endoplasmic reticulum protein that regulates bone mass homeostasis.","date":"2014","source":"Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research","url":"https://pubmed.ncbi.nlm.nih.gov/23959653","citation_count":20,"is_preprint":false},{"pmid":"32018225","id":"PMC_32018225","title":"Knockdown of P3H4 inhibits proliferation and invasion of bladder cancer.","date":"2020","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/32018225","citation_count":17,"is_preprint":false},{"pmid":"37979898","id":"PMC_37979898","title":"METTL3 regulates the proliferation, metastasis and EMT progression of bladder cancer through P3H4.","date":"2023","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/37979898","citation_count":14,"is_preprint":false},{"pmid":"33915904","id":"PMC_33915904","title":"Germinated Rhynchosia nulubilis Fermented with Lactobacillus pentosus SC65 Reduces Particulate Matter Induced Type II Alveolar Epithelial Apoptotic Cell Death.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33915904","citation_count":10,"is_preprint":false},{"pmid":"32750462","id":"PMC_32750462","title":"Germinated black soybean fermented with Lactobacillus pentosus SC65 alleviates DNFB-induced delayed-type hypersensitivity in C57BL/6N mice.","date":"2020","source":"Journal of ethnopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32750462","citation_count":10,"is_preprint":false},{"pmid":"30178839","id":"PMC_30178839","title":"P3H4 affects renal carcinoma through up-regulating miR-1/133a.","date":"2018","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30178839","citation_count":5,"is_preprint":false},{"pmid":"36297587","id":"PMC_36297587","title":"Efficient Delivery of P3H4 siRNA and Chlorin e6 by cRGDfK-Installed Polyarginine Nanoparticles for Tumor-Targeting Therapy of Bladder Cancer.","date":"2022","source":"Pharmaceutics","url":"https://pubmed.ncbi.nlm.nih.gov/36297587","citation_count":3,"is_preprint":false},{"pmid":"35805016","id":"PMC_35805016","title":"P3H4 Promotes Malignant Progression of Lung Adenocarcinoma via Interaction with EGFR.","date":"2022","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/35805016","citation_count":3,"is_preprint":false},{"pmid":"41220593","id":"PMC_41220593","title":"P3H4 Enhances the Proliferation, Invasion, and Glycolysis of Hepatocellular Carcinoma Cells.","date":"2025","source":"International journal of genomics","url":"https://pubmed.ncbi.nlm.nih.gov/41220593","citation_count":1,"is_preprint":false},{"pmid":"236823","id":"PMC_236823","title":"Stability and dissociation of P3H4-1 Burkitt's lymphoma cell soluble complement-fixing antigen identified with human serum.","date":"1975","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/236823","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8855,"output_tokens":1923,"usd":0.027705,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8856,"output_tokens":2714,"usd":0.056065,"stage2_stop_reason":"end_turn"},"total_usd":0.08377,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"SC65 (P3H4) is an endoplasmic reticulum-resident protein, not a nuclear or synaptonemal complex protein in somatic cells; its loss results in progressive osteopenia and a non-cell-autonomous increase in osteoclastogenesis, establishing SC65 as a negative regulator of bone resorption.\",\n      \"method\": \"Subcellular fractionation and immunofluorescence localization; Sc65 knockout mouse model with bone phenotyping (microCT, histomorphometry)\",\n      \"journal\": \"Journal of bone and mineral research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO mouse with defined cellular phenotype and direct ER localization experiment, single lab, two orthogonal methods\",\n      \"pmids\": [\"23959653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SC65 (P3H4) forms a complex in the ER with prolyl 3-hydroxylase 3 (P3H3); this complex regulates lysyl hydroxylase 1 (LH1) activity on collagen, potentially through interactions with LH1 and/or cyclophilin B. Loss of Sc65 destabilizes this complex, causing reduced collagen lysine hydroxylation and abnormal collagen cross-linking, leading to low bone mass and skin fragility.\",\n      \"method\": \"Sc65 knockout mouse model; co-immunoprecipitation of ER complex components; mass spectrometry-based collagen modification analysis; skeletal and connective tissue phenotyping\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP identifying complex members, KO mouse with defined molecular and tissue phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"27119146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SC65 (P3H4) and P3H3 act in the same pathway to hydroxylate lysines specifically at helical domain cross-linking sites in collagens I, across multiple tissues (skin, bone, tendon, aorta, cornea); neither SC65 nor P3H3 loss affects prolyl 3-hydroxylation at any known 3-hydroxyproline site. Loss of either protein alters divalent aldimine cross-link chemistry and reverses the HP/LP mature cross-link ratio in bone, phenocopying EDS VIA (PLOD1 deficiency).\",\n      \"method\": \"Tandem mass spectrometry on collagen from Sc65-/- and P3h3-/- mouse tissues; SDS-PAGE analysis of collagen cross-linked trimers; quantitative cross-link analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — quantitative MS-based substrate mapping in two independent KO models with orthogonal biochemical validation, replicated across multiple tissue types\",\n      \"pmids\": [\"28115524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ETV4 directly binds the promoter region of P3H4 and activates its transcription in bladder cancer cells; P3H4 knockdown inhibits bladder cancer cell proliferation, cell cycle progression, migration, and invasion in vitro and tumor growth in vivo, and overexpression of ETV4 rescues the inhibitory effects of P3H4 silencing.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP) and promoter reporter assays for ETV4 binding; shRNA knockdown of P3H4; rescue experiments with ETV4 overexpression; xenograft tumor model\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating direct promoter binding, genetic rescue experiment, in vivo xenograft, single lab\",\n      \"pmids\": [\"32018225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"P3H4 interacts with EGFR to promote malignant progression (metastasis and proliferation) of lung adenocarcinoma, with P3H4 modulating metabolic substances in this context.\",\n      \"method\": \"Co-immunoprecipitation/interaction assay between P3H4 and EGFR; P3H4 knockdown/overexpression in LUAD cell lines; in vivo tumor models\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP/pulldown reported in abstract without detailed mechanistic follow-up, single lab, limited methodological detail\",\n      \"pmids\": [\"35805016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"METTL3 (an m6A methyltransferase) regulates the mRNA stability of P3H4 in bladder cancer; METTL3 knockdown reduces P3H4 mRNA half-life, and overexpression of P3H4 rescues the inhibitory effects of METTL3 knockdown on bladder cancer cell proliferation, migration, invasion, and EMT.\",\n      \"method\": \"RNA stability assays measuring P3H4 mRNA half-life after METTL3 knockdown; shRNA knockdown and overexpression rescue experiments; in vivo xenograft with IHC\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA stability assay directly measuring mRNA half-life, genetic rescue experiment, in vivo validation, single lab\",\n      \"pmids\": [\"37979898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"P3H4 knockdown in hepatocellular carcinoma cells suppresses PI3K/AKT pathway phosphorylation and inhibits proliferation, invasion, and glycolysis (reduced glucose consumption, lactate, and ATP production).\",\n      \"method\": \"shRNA knockdown of P3H4; CCK8 viability assay; glycolysis detection kit measuring glucose/lactate/ATP; western blot for PI3K/AKT phosphorylation; nude mouse xenograft with IHC\",\n      \"journal\": \"International journal of genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, pathway placement inferred from phosphorylation changes without direct mechanistic link to P3H4's enzymatic/binding activity\",\n      \"pmids\": [\"41220593\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"P3H4 (SC65) is an ER-resident, non-enzymatic member of the leprecan family that forms a stable complex with prolyl 3-hydroxylase 3 (P3H3) and cyclophilin B; this complex is required for lysyl hydroxylase 1 (LH1) to hydroxylate lysine residues at helical cross-linking sites in fibrillar collagens across multiple tissues, and loss of P3H4 causes collagen lysine under-hydroxylation, aberrant cross-link chemistry phenocopying EDS VIA, low bone mass, and skin fragility, while in cancer contexts its transcription is driven by ETV4 and its mRNA stability is regulated by METTL3-mediated m6A modification.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"P3H4 (SC65) is an endoplasmic reticulum-resident protein that functions in collagen post-translational modification rather than in the nuclear/synaptonemal roles once attributed to it [#0]. In the ER it forms a stable complex with prolyl 3-hydroxylase 3 (P3H3), and this complex regulates the activity of lysyl hydroxylase 1 (LH1) on collagen, potentially through interactions involving LH1 and cyclophilin B [#1]. P3H4 and P3H3 act together specifically to hydroxylate lysines at helical-domain cross-linking sites in fibrillar collagens across skin, bone, tendon, aorta, and cornea, without affecting prolyl 3-hydroxylation; loss of either protein alters divalent aldimine cross-link chemistry and reverses the bone mature cross-link ratio, phenocopying EDS VIA (PLOD1 deficiency) [#2]. Consistent with this biochemical role, loss of P3H4 destabilizes the ER complex and produces collagen lysine under-hydroxylation, low bone mass, and skin fragility, with progressive osteopenia driven by non-cell-autonomous increased osteoclastogenesis [#0, #1]. In cancer contexts, P3H4 transcription is directly activated by ETV4 in bladder cancer, where it supports proliferation, cell-cycle progression, migration, and invasion [#3], and its mRNA stability is regulated by METTL3-mediated m6A modification [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Established that SC65/P3H4 is an ER-resident protein in somatic cells rather than a nuclear synaptonemal-complex component, reassigning its cellular compartment and linking it to skeletal homeostasis.\",\n      \"evidence\": \"Subcellular fractionation and immunofluorescence plus Sc65 knockout mouse bone phenotyping (microCT, histomorphometry)\",\n      \"pmids\": [\"23959653\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism connecting ER localization to the osteoclast phenotype not defined\", \"Non-cell-autonomous signal driving osteoclastogenesis not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the molecular partnership: SC65/P3H4 forms an ER complex with P3H3 that regulates LH1-mediated collagen lysine hydroxylation, explaining the bone and skin phenotypes.\",\n      \"evidence\": \"Co-immunoprecipitation of ER complex components, MS-based collagen modification analysis, and connective-tissue phenotyping in Sc65 knockout mice\",\n      \"pmids\": [\"27119146\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct enzymatic role of P3H4 within the complex not established (non-enzymatic scaffold vs. catalytic)\", \"Precise stoichiometry and contributions of LH1 and cyclophilin B unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Mapped substrate specificity to helical-domain cross-linking lysines and showed the pathway controls cross-link chemistry, demonstrating that P3H4/P3H3 loss phenocopies EDS VIA.\",\n      \"evidence\": \"Tandem MS substrate mapping and quantitative cross-link analysis on collagen from Sc65-/- and P3h3-/- mouse tissues across multiple tissue types\",\n      \"pmids\": [\"28115524\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the complex confers site-specificity to LH1 at helical sites is unknown\", \"Whether human P3H4 mutations cause an EDS-like disorder not addressed in the corpus\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified an upstream transcriptional driver of P3H4 in cancer, showing ETV4 directly activates P3H4 to support bladder tumor cell growth and invasion.\",\n      \"evidence\": \"ChIP and promoter reporter assays, shRNA knockdown with ETV4-overexpression rescue, and xenograft tumor model in bladder cancer cells\",\n      \"pmids\": [\"32018225\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Effector mechanism linking P3H4 to proliferation/invasion not defined\", \"Relationship between cancer role and ER collagen function unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Proposed a non-collagen interaction by reporting P3H4 binding to EGFR in lung adenocarcinoma.\",\n      \"evidence\": \"Co-immunoprecipitation/interaction assay and knockdown/overexpression in LUAD cell lines with in vivo tumor models\",\n      \"pmids\": [\"35805016\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation or detailed mechanistic follow-up\", \"Direct vs. indirect EGFR association not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed post-transcriptional control of P3H4 in cancer, with METTL3-mediated m6A modification stabilizing P3H4 mRNA to promote bladder cancer phenotypes.\",\n      \"evidence\": \"mRNA half-life assays after METTL3 knockdown plus knockdown/overexpression rescue and in vivo xenograft with IHC\",\n      \"pmids\": [\"37979898\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific m6A sites on P3H4 mRNA not mapped\", \"Reader protein mediating stabilization not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked P3H4 to a signaling/metabolic output in hepatocellular carcinoma via PI3K/AKT and glycolysis.\",\n      \"evidence\": \"shRNA knockdown with viability, glycolysis (glucose/lactate/ATP), and PI3K/AKT phospho-western readouts plus nude mouse xenograft\",\n      \"pmids\": [\"41220593\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway placement inferred from phosphorylation changes without direct mechanistic link to P3H4 activity\", \"Connection to ER collagen-modifying function unexplained\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How P3H4's defined ER collagen-modifying role mechanistically relates to its reported oncogenic functions, and whether human P3H4 variants cause connective-tissue disease, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No reconciliation between scaffolding role in collagen hydroxylation and cancer signaling functions\", \"No human genetic disease evidence in the corpus\", \"No structural model of the P3H4/P3H3/LH1/cyclophilin B complex\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [\"ER P3H4-P3H3 collagen-modifying complex\"],\n    \"partners\": [\"P3H3\", \"LH1\", \"cyclophilin B\", \"ETV4\", \"METTL3\", \"EGFR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}